In such devices, inserts which are very sensitive to radial pressure and which are chiefly axially traversed ceramic substrates, are held in an outer housing by radial clamping. Between the ceramic insert and the outer housing, an insulation mat is arranged, which forms an elastic element. Various methods exist for so-called “canning,” i.e. for introducing or arranging the insert into the housing. Some of these methods will be explained below.
A first method for manufacturing the device is the so-called “calibrating” or “shrinking” method, where the insert with the insulation mat is put into an oversized, peripherally closed tube referred to as a jacket, and subsequently the unit obtained is placed in a tool. The tool is provided with numerous radially inwardly movable pressure jaws. When the pressure jaws are moved radially inwards, they plastically deform the jacket to such an extent that the insert is clamped in the jacket.
Another method for manufacturing the device is the so-called “stuffing” method, where the outer housing is first brought to the desired outer radius; and subsequently, the insert wrapped with the insulation mat is placed or introduced into the outer housing through a funnel-shaped tool.
Other methods include the so-called “wrapping” method, wherein a sheet metal is wrapped around the insert and welded in the desired end position in the overlap region of the sheet-metal edges, and the so-called “clamping” method, in which the housing is divided into two half-shells between which the insert is clamped.
An important characteristic of the insulation mats is the gap bulk density (GBD). It designates the compression of a certain mass of the material in the gap between insert and housing. Due to the resilience of the housing material, a lower GBD can be obtained by the canning method, so that the insulation mats must be compressed more during the canning method. A thermal expansion of the housing and hence a lower GBD in operation of the exhaust gas cleaning device must be compensated during the manufacture by a correspondingly greater compression of the housing and the insulation mat in the cold condition.
One objective is to create a machine tool for manufacturing an exhaust gas cleaning device and to provide a method for manufacturing exhaust gas cleaning devices by which the inserts are very safely held in the housing.